If springs in the form of tension springs must be used, it is necessary to provide them with lugs at both ends during production. Various lug forms are known, especially stem lugs (in which the lug sits on a stem progressing away from the spring element at a specific distance) as well as so-called “normal German lugs,” in which the lug sits directly, and without formation of an intermediate stem, on the applicable end of the spring element. During production of the lugs, the shaping of the second, i.e., rear lug (at the end of the spring element) is especially problematic, particularly during the production of German lugs.
The production of a first (front) lug on the uncut wire directly in the spring production machine, such as a spring coiling machine, no longer presents a problem when a vertical mill is used and can be implemented easily. This, however, does not apply to the production of the second lug, namely the object at the end of the spring element; various methods have been used previously for its formation which.
The solution to the problem is relatively simple when such a lug is manufactured as a stem lug. In this case, the spring element is gripped and held by gripping tongs provided on the spring production machine and then severed from the wire by means of a cutting device. The excess wire segment is then, similar to the production of the first lug, shaped into a second (rear) lug by means of a vertical mill.
The production of a second (rear) German lug, however, is significantly more complex and requires additional equipment. In this case the spring, as described above, is initially provided with a first lug, which does not prove to be problematic in the case of the front lug, even when it is formed as a German lug. Then the spring element is shaped (e.g., coiled). However, only a short piece of wire would be necessary to form the second, that is, rear lug, which, however, a pair of gripping tongs would no longer be able to grip in such a way that a vertical mill could be used. For this reason, the spring element, which consists of a number of shaped coils and the first lug, has previously been gripped by a separate pair of gripping tongs to form a rear German lug, and has then been conveyed to another processing station known as a “lug plate,” in which a second (German) lug could then be manufactured by setting up the last coil. However, a lug plate and a separate pair of gripping tongs are relatively costly additional devices and, furthermore, adjustment of a lug plate is rather complicated.
Based on the above, the goal of the invention is to find a method of the type mentioned initially, with which the production of the second (rear) lug, which may be one of a wide variety of lug types. In other words, also a German lug, can be creating using normal, standard tools, wherein operational safety is increased, and, as a whole, both the production process can be performed and the apparatus itself can also be manufactured more cost-effectively.